Endosteal guide pin, positioning trocar and trocar for removing said pin

ABSTRACT

An endosteal guide pin for preparing a guide path for the implantation of a pedicle or orthopaedic screw into a patient&#39;s bone. The pin has a head intended to be provisionally implanted in a bone and a guide rod, coaxial with and rigidly secured to the head, ending in a free end intended to be at least level with the skin surface of the patient when the pin is in the implanted position in the bone. The pin has a first coupling part intended at least to secure the pin to and release the pin from at least one portion of a positioning trocar and a second coupling part intended at least to secure the pin to a removal trocar. Also, a trocar for positioning a guide pin, which trocar incorporates the guide pin, and to a trocar for removing the pin.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of and is based upon andclaims the benefit or priority under 35 U.S.C. § 120 from U.S. Ser. No.16/489,491, filed Aug. 28, 2019, herein incorporated by reference, whichis a National Stage Application of International Application No.PCT/FR2018/050624, filed Mar. 15, 2018, which claims the benefit ofpriority under 35 U.S.C. § 119 from France Patent Application No.PCT/FR2017/050595.

FILED

The invention relates to the field of orthopaedic surgery and moreparticularly to the field of pedicle or orthopaedic screw implantation.

BACKGROUND

The implantation of pedicle screws in vertebrae is widely used inorthopaedic surgery, in particular to hold vertebrae in place and/or tostabilise fracture-type lesions. This technique is also referred to aspedicle screw spinal osteosynthesis.

Surgeries in this field have shown a recent evolution towards techniquesthat are less invasive than total exposure of the operating field. Thesenew so-called minimally invasive surgeries prevent blood loss and tissuelesions, and reduce the time under anaesthesia and risks of infection.Although these minimally invasive techniques require the production oftools adapted for a smaller cutaneous opening, the correct positioningof the pedicle screw and the absence of any neurological lesion mustalso be ensured. To achieve this, the surgery is coupled with imageguidance of the fluoroscopic, CT or MRI type for example, accompanyingthe guiding of the precise positioning of the pedicle screw.

The patent document WO2009091616 discloses a surgical tool for placing aprovisional guide pin used to guide the implantation of the definitivepedicle screws. The surgery can be performed on a patient in the laidback position on an imaging table, and under radiological guidance, forexample X-ray guidance. The tool primarily includes a positioning trocarat the end whereof a provisional guide pin is coaxially mounted suchthat it can be removed. A fixing rod is also mounted inside thepositioning trocar and the guide pin. This fixing rod includes a sharptip which, by projecting from the guide pin, allows said pin to beinserted. A sleeve equipped with a handle is also provided around thefixing rod and the positioning trocar. This tool enables the surgery tobe performed in two stages.

Firstly, the guide pin is inserted into the vertebra by means of thetool and more particularly thanks to the capacity to remove the pin fromthe rest of the tool, which enables the guide pin to be disengaged fromthe opposite end of the tool. The pin is thus the only element to remainin the vertebra and can be removed when positioning the screws. Thepedicle screw is thus fixed in the vertebra at the orifice previouslyprepared by the provisional guide pin.

The instrument described in this publication has a certain number ofdrawbacks. Firstly, this instrument is complex as a result of the numberof parts involved, which can generate difficulties in ensuring themaintenance of the guide pin in the screwed vertebra and which createsrisks of infection and excessively long surgery durations.

Moreover, the high number of manipulations as a result of the number ofparts involved in this tool requires a sufficiently large surgicalspace. However, the configuration of this instrument requires thesurgery, in its entirety, to be carried out with image guidance toensure the insertion of the guide pin, the removal thereof, and theinsertion and fixation of the pedicle screw. This results in a need fora large amount of space in a limited working space, for example a CTscanner.

Finally, the complexity of the tool increases the manufacturing costthereof.

SUMMARY

The invention relates to an instrument formed by a provisional guide pinand parts for inserting and removing this pin, which ensure the easyplacement of the guide pin as well as the subsequent placement of thepedicle screw, without being confronted with the aforementionedproblems.

In particular, the invention relates to an instrument whichcomprehensively provides improved precision and safety for the patient,without being subjected to the aforementioned spatial requirementissues.

The invention further relates to a simple instrument for a reducedmanufacturing cost.

Finally, the invention relates to an instrument that is capable of beingadapted to a method for implanting pedicle or orthopaedic screws,wherein the operations for placing the guide pin and for placing thepedicle screw can be separated.

The invention relates to the use of an endosteal guide pin for preparinga guide path for the implantation of a pedicle or orthopaedic screw,which pin is essentially characterised in that it includes a headintended to be provisionally implanted in a bone, and a guide rod,coaxial with and rigidly connected to the head, ending in a free endadapted such that it is at least flush with the skin surface of thepatient when the pin is in the implanted position in the bone, which pinincludes a first coupling means intended at least to ensure the rigidconnection thereof to and the disconnection thereof from at least onepart of a positioning trocar, and a second coupling means intended atleast to ensure the rigid connection thereof to a removal trocar.

The guide pin of the invention can further include the followingoptional features, considered singly or according to any combinationstechnically possible:

-   -   the guide rod of said pin is capable of being cut so that the        end thereof is located beneath and in the vicinity of the skin        surface when the pin is in the implanted position in the bone;    -   at least one part of the head has a circular section with an        average diameter D1, and the guide rod has a circular section        with an average diameter D2 that is less than the diameter D1 of        the head;    -   the guide pin is made of stainless steel or titanium, and the        diameter D2 of the guide rod is less than 2 millimetres;    -   the head has a free end formed by a bevel, double bevel or        diamond tip;    -   the first coupling means comprises a threading produced on the        guide rod;    -   the threading is produced away from the head;    -   the first coupling means further comprises a rotation locking        element;    -   the rotation locking element is produced at the head;    -   the rotation locking element is in the vicinity of the rod;    -   the locking element has a polygon-shaped section, for example a        hexagonal section;    -   the second coupling means is formed by a threading produced on        the head;    -   the threading is produced at the locking element;    -   the locking element includes a smooth part and a threaded part        also forming a second coupling means;    -   the first and second coupling means are aligned.

The invention further relates to a trocar for placing an endosteal guidepin, which is essentially characterised in that it includes a first partcomprising the guide pin, said pin including a head intended to beprovisionally implanted in a bone, and a guide rod, coaxial with andrigidly connected to the head, ending in a free end, and adapted suchthat it is at least flush with the skin surface of the patient when thepin is in the implanted position in the bone, the positioning trocarfurther comprising a second hollow part to which the first part iscoupled in a removable manner by means of a rigid connection systemincluding a first coupling means provided on said pin and a cooperatingcoupling means provided on the positioning trocar, the guide rod of theguide pin being fitted inside the hollow part such that it slides, andin that the pin includes a second coupling means intended at least toensure the rigid connection thereof to a removal trocar.

Advantageously, the free end of the hollow part includes driving meansfor driving the guide head into the bone, in particular rotating and,where appropriate, grasping means.

Preferably, the first coupling means of the removable rigid connectionsystem includes a threading made away from the head of the guide pin,and in that the cooperating coupling means includes a tapping coincidentwith said threading.

More preferentially, the tapping is produced in a nut disposed coaxiallyto said hollow part of the positioning trocar, which nut cooperates withthe threading such that the rotation of the nut drives the screwing orunscrewing of the guide rod of the pin relative to the rest of thepositioning trocar in order to enable the guide pin to be rigidlyconnected to or disconnected from the second hollow part of thepositioning trocar.

Preferentially, the tapping is located at the driving means of thepositioning trocar.

Advantageously, the removable rigid connection system further includes arotation locking element provided on the pin and a cooperating lockingelement provided in the hollow part of the trocar in order to preventthe rotation of the guide pin relative to the hollow part of thepositioning trocar around the axis of said positioning trocar.

More preferentially, the rotation locking element is provided at thehead of the pin.

Advantageously, the rotation locking element is located in the vicinityof the rod.

Preferably, the locking element has a polygon-shaped section, forexample a hexagonal section, and in that the cooperating locking elementis formed by a key made in the hollow part of the trocar and adapted forcooperating with the first locking element.

The invention further relates to a trocar for removing an endostealguide pin for preparing a guide path for the implantation of a pedicleor orthopaedic screw, the pin including a head intended to beprovisionally implanted in a bone, and a guide rod, coaxial with andrigidly connected to the head, ending in a free end adapted such that itis at least flush with the skin surface of the patient when the pin isin the implanted position in the bone, which pin includes a firstcoupling means intended to ensure the rigid connection thereof to andthe disconnection thereof from at least one part of a positioningtrocar, and a second coupling means intended at least to ensure therigid connection thereof to a removal trocar, characterised in that itincludes a hollow fixing rod intended to be fitted around the guide rodof said pin, and a coupling means cooperating with the second couplingmeans of said pin to form a removable rigid connection system enablingthe guide pin to be removed when the second coupling means of the pinand the cooperating coupling means of the hollow rod of the removaltrocar are assembled together.

Advantageously, the cooperating coupling means is formed by a tappingmade on the inside face of the hollow rod, and which is capable of beingassembled with the second coupling means of the guide pin formed by athreading made on the guide rod or on the end part of the head rigidlyconnected to the guide rod.

The invention further relates to a method for preparing a guide path forimplanting a pedicle or orthopaedic screw, comprising the followingsteps of:

a. Inserting the positioning trocar described hereinabove;

b. Disconnecting and removing the second hollow part of the positioningtrocar so as to only leave the pin implanted in the bone;

c. Cutting the free end of the rod of the pin such that the cut rod islocated beneath and in the vicinity of the skin surface.

Preferentially, the method comprises an additional step of placing theremoval trocar described hereinabove and of rigidly connecting same tothe guide pin by the removable rigid connection system considered,followed by a step of removing the pin using the removal trocar.

Advantageously, the step of disconnecting the hollow part of thepositioning trocar is carried out by unscrewing the nut from thethreading of the free end of the rod, followed by the removal bytranslation along the axis of the rod of said hollow part.

Preferably, the placement of the removal trocar is carried out byscrewing said trocar around the threading produced on the rod or on thehead of the pin.

BRIEF DESCRIPTION OF THE FIGURES

Other characteristics and advantages of the invention will clearlyemerge from the following description, which is given as a rough guideand in no way as a limited guide, with reference to the appendedfigures, from which:

FIG. 1 is a diagrammatic side view of the guide pin of the inventionaccording to a first alternative embodiment,

FIG. 2 is a diagrammatic side view of a guide pin positioning trocar ofthe invention according to a first configuration integrating, in thefirst part, said pin in FIG. 1, and shown when the pin is rigidlyconnected to the positioning trocar,

FIG. 3 is a diagrammatic side view of the guide pin positioning trocarof the invention in FIG. 2, shown when the pin is disassembled from thepositioning trocar,

FIG. 4 is a diagrammatic side view of the removal trocar of theinvention according to a first configuration, fitted around the guiderod of the pin of the invention in FIG. 1 and according to anintermediate disassembly position.

FIGS. 5 to 12 show the operations for implanting in a vertebra and forremoving the pin of the invention of the first alternative embodimentshown in FIG. 1, using the positioning trocar according to the firstconfiguration shown in FIGS. 2 and 3, and the removal trocar accordingto the first configuration shown in FIG. 4.

FIG. 5 is a diagrammatic view of a first step of placing the guide pinin a vertebra, in which step the first part of the positioning trocarformed by the head of the pin of the invention is implanted in thevertebra,

FIG. 6 is a diagrammatic view of a second step of placing the guide pinin a vertebra, in which step the hollow part of the positioning trocarhas been disassembled from the guide pin and is extracted,

FIG. 7 is a diagrammatic view of the guide pin in place in the vertebra,the guide rod of the pin projecting from the skin surface,

FIG. 8 is a diagrammatic view of a third step of placing the guide pinin a vertebra, wherein the guide rod of the pin is cut beneath and inthe vicinity of the skin surface,

FIG. 9 is a diagrammatic view of a first step of removing the pininvolving the prior placement of an external sheath and showing theinsertion of a removal trocar according to the invention around theguide rod of the pin in position,

FIG. 10 is a diagrammatic view of a second step of removing the pin, inwhich step the removal trocar is rigidly connected to the pin,

FIG. 11 is a diagrammatic view of a second step of removing the pin, inwhich step the removal trocar and the pin are extracted,

FIG. 12 is a diagrammatic view of the external sheath in position forguiding the operator for the placement of a pedicle screw,

FIG. 13 is a diagrammatic view identical to that of FIG. 3 showing atrocar for positioning a guide pin according to one advantageousconfiguration wherein the hollow part of this positioning trocar forms aremoval trocar,

FIG. 14 is a diagrammatic side view of the guide pin of the inventionaccording to a second alternative embodiment,

FIG. 15 is a diagrammatic side view of a guide pin positioning trocar ofthe invention according to a second configuration integrating, in thefirst part, the pin in FIG. 14, and shown when the pin is rigidlyconnected to the positioning trocar,

FIG. 16 is a diagrammatic side view of a guide pin positioning trocar ofthe invention according to a third configuration integrating, in thefirst part, the pin in FIG. 14, and shown when the pin is rigidlyconnected to the positioning trocar,

FIG. 17 is a diagrammatic side view of a guide pin positioning trocar ofthe invention according to a fourth configuration,

FIG. 18 is a longitudinal sectional view of the positioning trocar inFIG. 17,

FIG. 19 is a longitudinal sectional view of a feature in FIG. 17,showing the hollow part of the positioning trocar,

FIG. 20 is a longitudinal sectional view of the head of the guide pin inFIG. 17,

FIG. 21 is an overhead view of the head of the guide pin in FIG. 17, and

FIG. 22 is a perspective view of one part of the head of the guide pinin FIG. 17, in particular showing the junction portion with the guiderod, a hexagonal locking element and the second coupling means formed bya hexagonal threading.

DETAILED DESCRIPTION

The instrument of the invention firstly provides an endosteal guide pinhaving an unprecedented configuration which has a coaxial extension ofthe pin head capable of extending beneath and in the vicinity of theskin surface of the patient when the head is impacted in the bone. Thus,the operator can easily relocate the pin in order to place the pediclescrew.

The instrument of the invention further provides a positioning trocarwhich integrates said guide pin. More particularly, the positioningtrocar comprises a first part formed by the guide pin and a second partincluding at least one hollow rod. The first part comprises a distalpart of the positioning trocar formed by the head of the guide pin. Theend of this distal part, and thus the free end of the head of the pin,can include a single bevel tip, or preferably a double bevel tip, whichboth enables single cutaneous passage when inserting the trocar andoptimised impact of the pin in the bone. Alternatively, the free end ofthe head of the pin is a diamond tip, particularly suited for implantingthe head of the pin with a positioning trocar associated with a powereddriving system. The integration of the tip in the pin removes the needto use a fixing rod provided in the system of the prior art describedhereinabove.

Moreover, the pin and the rest of the trocar are rigidly connected bycoupling means which can be, for the alternative embodiment shown inFIGS. 1 to 12, a bayonet rigid connection system. This system does notresult in the mechanical strength issues of the thread pitch of the pinholder of the prior art, which allows the insertion of the positioningtrocar and the implantation of the pin in the bone to be power-assisted.Other fixing means can be provided, for example a threading/tappingsystem and nut located in the vicinity of the free end of the secondpart or hollow part of the positioning trocar (FIGS. 14 to 16) with,where appropriate, locking means preventing any rotational movement ofthe guide pin along the axis thereof relative to the rest of thepositioning trocar (FIGS. 20 to 22).

Finally, the instrument according to the invention further provides atrocar for removing the pin. According to one alternative embodiment,this removal trocar can be formed by the second part of the positioningtrocar. In this scenario, the comprehensive instrument includes thesecond part of a positioning trocar also forming a removal trocar, andthe guide pin forming a first part of the positioning trocar and thehead whereof forms a distal part of the positioning trocar. Theinstrument is thus formed by only two parts.

The instrument of the invention allows the operations of placing theguide pin and of placing the pedicle screw to be separated. The guidepin can thus, for example, be placed by a first operator with imageguidance, then the patient can be transported to another location. Theoperations of removing the guide pin and fixing the pedicle screw can becarried out by a second operator, in another location, for example in anoperating room, without image guidance. Thus, in order to position theguide pin, image guidance devices that are not available in theoperating room can be used. Moreover, the positioning of the pediclescrew is not subjected to restricted spatial requirements.

With reference to FIG. 1, the guide pin of the invention 1 includes ahead 2 having a circular section with a diameter D1 and ending, at thefree end thereof, in a double bevel tip 3 or a diamond tip. The pin 1extends on the side opposite the tip 3 by a coaxial guide rod 4 having acircular section with a diameter D2 that is less than the diameter D1 ofthe head 2 and ending in a free end 5. The guide pin 1 thus extendslongitudinally from the tip 3 of the head 2 to the free end 5 of theguide rod 4.

The end opposite the tip 3 of the head 2 includes a first coupling meansformed by the male part 6 of a bayonet rigid connection system which isintended to cooperate with the female part of this system provided onthe hollow part of the positioning trocar which will be describedhereafter.

The guide rod 4 includes a second coupling means formed by a threading 7intended to cooperate with a tapping provided on the removal trocar ofthe invention which will be described hereafter. Alternatively, as shownin FIGS. 17 to 22, the threading 7 b intended to cooperate with thetapping of the removal trocar is produced on a part of the head 2 b ofthe guide pin located in the vicinity of the guide rod 4 b.

The guide pin is made of a metal material, for example of stainlesssteel or titanium. By way of illustration, the overall length of the pinis 150 millimetres, the diameter D1 is 2.4 millimetres and the diameterD2 is 1 millimeter. The length of the guide rod 4 is at least 100millimetres in order to project from or at least lie flush with the skinsurface when the head of the pin is in the implanted position in thebone (before any cutting operation is carried out on the guide rod).

With reference to FIGS. 2 and 3, the positioning trocar of the invention8 includes a second so-called hollow part formed by a hollow rod 9 andending in a grasping and driving handle 9 a. This handle 9 a allows thepositioning trocar 8 to be manually inserted and removed. In place ofthis handle 9 a, means for cooperating with a power tool can be providedfor the power-assisted placement and removal of the trocar 8. Such meansfor cooperating with a power tool are shown in FIGS. 17 to 19, and areformed by a rotating member 29 rigidly connected to the free end of thehollow part of the positioning trocar 8 c and intended to cooperate withthe end piece forming a key of the power tool, for example a powerscrewdriver. In order to ensure the engagement of the rotating member 29with the end piece of the screwdriver, said member 29 has apolygon-shaped section, preferentially a hexagonal section.

At the opposite end of the handle 9 a, the hollow part 9 extendscoaxially by a first part formed by the pin 1, the guide rod 4 whereofis fitted inside the hollow part 9 of the trocar 8 such that it slides.

Moreover and with reference to FIG. 3, the end of the hollow part 9 ofthe trocar 8 opposite the handle 9 a has a female part 10 of a bayonetrigid connection system which cooperates with the male part 6 located atthe end of the head 2 of the pin 1. The cooperation of these two parts6, 10 forms (FIG. 2) the bayonet rigid connection system 11 enabling thehollow part 9 of the positioning trocar 8 to be rigidly connected to anddisconnected, by rotation and longitudinal removal, from the pin 1.

Thus, the positioning trocar 8 integrates the guide pin 1 in FIG. 1which is, via the bayonet rigid connection system 11, rigidly connectedto or disconnected from the hollow part 9 of the trocar 8.

With reference to FIG. 4, the trocar for removing the pin 12 accordingto a first alternative embodiment is made of a hollow rod 13 ending, atone of the ends thereof, in a grasping handle 14. In place of thishandle 14, means for cooperating with a power tool can be provided forthe power-assisted placement and removal of the trocar 12, for examplemeans identical to those described hereinabove relative to the hollowpart of the positioning trocar.

At the opposite end of the handle 14, the internal circumference of thehollow tube 13 includes a tapping 15 which is capable of cooperatingwith the threading 7 provided on the guide rod 4 of the pin 1 and in thevicinity of the head 2 thereof. The internal diameter of the hollow tube13 of the removal trocar 12 is thus adapted to the fitting of theremoval trocar 12 around the guide rod 4 of the pin 1 and to thecooperation of the tapping 15 with the threading 7. The externaldiameter of the hollow tube is not subjected to any restrictions asregards the cooperation thereof with the pin 1. Alternatively, theremoval trocar and the tapping thereof are adapted to cooperate with thethreading 7 b made on the head 2 b of the guide pin, in the vicinity ofthe guide rod 4 b (FIGS. 17 to 22).

Reference is made to FIGS. 5 to 12 to describe the different steps ofplacing the provisional pin 1 in the bone and of removing this pin,which are carried out by an operator or by two operators beforeimplanting the pedicle or orthopaedic screw.

In FIG. 5, the positioning trocar 8 provided, at the end thereof, withthe pin 1 is easily inserted according to the arrow F1 thanks to thedouble bevel tip 3. The pin is driven into the bone 16 manually or withpower assistance, and the handle 10 of the positioning trocar 8naturally projects from the skin surface 17, as well as the end 5 of theguide rod 4 of the pin 1.

In FIG. 6, the removal of the hollow part 9 of the positioning trocar 8is carried out by turning the handle 9 a of the positioning trocar 8 inthe anticlockwise direction according to the arrow F2 in order todisconnect the male and female parts of the bayonet rigid connectionsystem 11 and disengage the pin 1 from the hollow part 9 of thepositioning trocar 8, then by applying a tensile force according to thearrow F3.

As shown in FIG. 7, the pin 1 thus remains in place in the bone 16, theend 5 of the guide rod 4 projecting from the skin surface 17.

A suitable tool, for example surgical nippers, is then used to cut theend region of the guide rod 4 such that the new end 5 a is locatedbeneath and in the vicinity of the skin surface 17. This positioning onthe one hand allows the operator or a second operator to relocate thisend by simple palpation, and on the other hand prevents any risk ofinfection if the patient is transferred to a second location for theremaining operations.

All of these operations described with reference to FIGS. 5 to 8, andmore particularly those of FIGS. 5 and 6, are preferably carried outwith image, CT, X-ray or MRI guidance, by a radiologist. The position ofthe pin 1 in the bone is thus perfectly controlled.

Once the guide pin 1 is in position, the patient can be transported to asecond location, which no longer requires any imaging device, forexample an operating room. The operator can even be the same operator asthe operator that fixed the guide pin, or another operator, for examplea surgeon.

The placement of the pedicle screw by the operator begins by palpatingthe skin of the patient to locate the cut end 5 a of the guide rod 4 ofthe pin 1. Once this end 5 a has been located, the operator inserts anexternal sheath 18 around the guide pin 1.

The surgeon then inserts into the external sheath 18, around the guiderod 4 of the pin 1 and according to the arrow F4, the removal trocar 12towards the head 2 of the pin 1.

With reference to FIG. 10, the removal trocar 12 is then rigidlyconnected to the pin by screwing in the clockwise direction according tothe arrow F5 and by cooperation between the threading 7 on the guide rod4 or the head 2 of the pin 1 and the tapping 15 on the inside face ofthe hollow tube 13 of the removal trocar 12.

With the removal trocar 12 and the guide pin 1 thus rigidly connected toone another, these two parts are extracted by manual or power-assistedgrasping according to the arrow F5 (FIG. 11). Only the external sheath18 then remains (FIG. 12), allowing the operator to insert and impact anew pin or a pedicle screw according to the trajectory of the guide pin.

FIG. 13 shows an advantageous alternative embodiment for producing theinstrument of the invention, wherein the pin 1 a is identical to the pin1 in FIG. 4, with the exception that it does not include the threading7. More specifically, in this alternative embodiment, the part (in thiscase the male part) of the bayonet rigid connection system forms boththe first and second coupling elements. As a whole, and for all of thealternative embodiments of the invention, the first and second couplingmeans are aligned when the removal trocar is identical to the secondpart of the positioning trocar (8, 8 b, 8 c).

When the pin has this configuration, the hollow part 9 of thepositioning trocar 8 (which is identical to that in FIGS. 2 and 3) thusforms a removal trocar 12 a for which the hollow rod 13 a does notinclude any tapping, the part 10 (in this case the female part) of thebayonet rigid connection system 11 allowing the rigid connection of theremoval trocar 12 a with the pin 1 for the extraction of this pin 1.

This configuration has the advantage of providing a comprehensiveinstrument that overcomes all of the aforementioned drawbacks using onlytwo parts: the pin of the invention, and a trocar (removal trocar),otherwise referred to as the hollow part of the positioning trocarrigidly connected in a removable manner to said pin 1.

In an alternative embodiment shown in FIGS. 14 to 16, the removablerigid connection system 20 of the hollow part 9 of the positioningtrocar 8 b with the pin 1 b includes a threading 21 located at the freeend 5 of the guide rod 4 of the pin 1 b which cooperates with a nut 22located at the grasping handle 9 a of the positioning trocar 8 b via atapping (not shown in the figures) made on the hollow inside face of thenut 22. Thus, the disconnection of the hollow part 9 from the pin 1 btakes place by rotation of the nut 22, which prevents any risk, duringthis disconnection, of the head 2 of the pin 1 b from rotating arounditself when the patient suffers from a certain bone fragility.

Alternatively to this alternative embodiment shown in FIGS. 17 to 19,the tapped nut 24 forming a part of the positioning trocar 8 c isdisconnected from the hollow part of said positioning trocar 8 c, or atleast is entirely free to rotate relative to the hollow part, as will bedescribed in more detail hereinbelow.

With reference to FIGS. 17 to 22, another embodiment of the guide pin 1c and of the positioning trocar 8 c according to the invention will nowbe described.

Similarly to the embodiment of the positioning trocar 8 relative toFIGS. 2 and 3, the positioning trocar 8 c relative to FIGS. 17 to 19comprises the guide pin 1 c and the hollow part 13 b.

The head 2 b of the guide pin 1 c comprises, at the free end thereof,the tip 3 b intended to penetrate the bone during implantation. This tip3 b comprises a double bevel machining easing the penetration of thehead 2 b into the bone. Alternatively, this tip 3 b is a diamond tip.The head 2 b comprises, at the opposite end thereof, a blind orifice 32(see FIGS. 20 to 22), the section whereof is circular or polygonal forexample, wherein the guide rod 4 c is intended to be inserted andrigidly connected to said head 2 b. In one possible alternativeembodiment, the head 2 b and the rod 4 b are in one piece. The guidehead 2 b further comprises a portion 31, the section whereof ispolygon-shaped, as well as a threading 7 b forming a second couplingmeans with the removal trocar, which will be described hereinbelow.

The guide rod 4 b of the pin 1 c is threaded over a portion that isremote from the head of the pin. Given that this threading 21 b isintended to cooperate with the tapped nut 24 which is a bolt 24 in thisembodiment, it thus forms a first part of the coupling means 6 betweenthe guide pin 1 c and the hollow part 13 b of the positioning trocar 8c. Preferentially, the length of the guide rod 4 b is adapted such thatthe threading 21 b is made at the free end 5 b of said rod 4 b.Nonetheless, the coaxial orifice of the bolt 24, wherein the tapping 25intended to cooperate with the threading 21 b of the first couplingmeans 6 is made, can be penetrating so as to allow said bolt 24 to berigidly connected to a rod 4 b, the length whereof is greater than thehollow part 13 b of the positioning trocar.

Moreover, the portion 31 of the guide head 2 b having a polygonalprofile section, that is for example hexagonal, is preferentially remotefrom the tip 3 b, the rest of the head 28 having a circular section.Moreover, the diameter of the portion having a circular section 28 isgreater than the diameter of the portion having a polygonal section 31:a shoulder 33 is thus present at the junction between the portion havinga circular section 28 and the portion having a polygonal section 31.

The portion having a polygonal section 31 made on the head 2 b forms anelement for locking the rotation of said head 2 b relative to the hollowpart 13 b of the positioning trocar 8 c, when this hollow part isengaged on the guide pin 1 c. This locking element 31 forms the secondpart of the coupling means 6 of the guide pin 1 c.

The locking element 31 of the guide pin 1 c is intended to cooperatewith a key 26 made in the hollow part 13 b of the positioning trocar 8c, which, following the example of the positioning trocar 8 in FIGS. 2and 3, comprises a hollow rod ending in grasping and driving means,these means being capable of being a handle or a rotating member 29intended to cooperate with a power tool. Thus, the polygonal key 26 ofthe positioning trocar 8 c is made at the end of the hollow part 13 b ofsaid trocar 8 c opposite the grasping and driving means. The key 26 isitself extended by a cylindrical tube portion 27, the inside diameterwhereof is greater than the inside diameter of the polygonal key 26. Ashoulder 34 is thus present at the junction between the tube portion 27and the polygonal key 26.

When the hollow part 13 b of the positioning trocar 8 c is fitted ontothe guide rod 4 b of the pin 1 c such that it slides, the tube portion27 of said hollow part 13 b of the trocar engages around the portionhaving a circular section 28 of the head, and the polygonal key 26engages around the element 31 for locking the rotation of the head 2 bof the pin 1 c, which enables any rotation of the pin 1 c relative tothe rest of the trocar 8 c to be locked. Moreover, the two shoulders 33,34 come to bear against and make contact with one another when the pin 1c and the rest of the positioning trocar 8 c are in the correct positionfor the rigid connection thereof. The bolt 24 is thus screwed around thecorresponding threading 21 b of the guide rod 4 b and forming part ofthe first coupling means 6 for rigidly securing the pin 1 c to thehollow part 13 b of the positioning trocar in order to form thepositioning trocar 8 c. The combined effect of the contact between theshoulders 33, 34, of the engagement of the key 26 around the polygonalportion 31 of the head 2 b and the placement of the bolt 24 around therod 4 b completely locks the translation and rotation of the guide pin 1c relative to the rest of the positioning trocar. Thus, the removablerigid connection system of the positioning trocar 8 c is formed by thethreading 21 b of the rod 4 b, the hexagonal portion 31 of the head 2 b,the key 26 and the tapping 25 of the bolt 24.

With reference to FIGS. 18 and 19, when the grasping and driving meansare formed by the polygonal rotating member 29 intended to cooperatewith a power tool, the bolt 24 is arranged such that it engages in acylindrical recess 30 made in the wall of said rotating member 29, suchthat the bolt 24 is disposed coaxially to said rotating member 29 andthus to the hollow part 13 b of the positioning trocar 8 c. This bolt24, which has a substantially cylindrical shape, can be entirelydisconnected from the hollow part 13 b of the positioning trocar 8 cwhen it is not screwed onto the rod 4 b. Alternatively, the bolt 24 canbe mounted such that it rotates in the recess considered 30, for exampleusing a flange (not shown) projecting from the cylindrical wall 35 ofthe recess 30 and cooperating with a groove (not shown) made in thecylindrical wall of the bolt 24. This specific arrangement prevents theloss of the bolt 24 and enables the pin 1 c to be fixed to the hollowpart 13 b of the positioning trocar 8 c without any rotation takingplace between the pin 1 c and the hollow part 13 b of the trocar 8 c.

Finally, the guide pin 1 c comprises a threading 7 b forming the secondcoupling means, intended to cooperate with the removal trocar.

This threading 7 b can be made, as described hereinabove, on the rod 4 bof the guide pin 1 c. Advantageously, in the embodiment shown in FIGS.17 to 22, the threading 7 b is made on a portion of the head close tothe rod 4 b, and more preferentially on the portion having a polygonalsection 31 such that this section 31 comprises the threading 7 b and ahexagonal smooth part 23, as shown in particular in FIG. 22.

In this manner, the threading 7 b has a dual purpose: that of formingthe second coupling means of the guide pin 1 c with the removal trocar,and that of ensuring, with the smooth part having a polygonal section23, the locking of the rotation of the pin 1 c relative to the rest ofthe positioning trocar 8 c. The production of the threading 7 b on theportion having a polygonal section 31 thus allows advantage to be takenof the length of said threading 7 b in the overall length of the portionhaving a polygonal section 31, which ensures a particularly stable andeffective engagement of the pin 1 c with the hollow part 13 b of thepositioning trocar 8 c, with the generation of maximum leverage when thepractitioner exerts a rotational movement on the positioning trocar 8 cin order to implant the guide head 2 b in the bone.

According to another alternative embodiment shown in FIG. 16, the hollowpart 9 of the positioning trocar 8 b can extend longitudinally as far asthe end 3 of the head 2 of the pin, while having a diameter that isgreater than the diameter D1 of the head 2 of the pin 1 b.

Similarly to the alternative embodiment shown in FIG. 13, the hollowpart of the positioning trocar 8 b can be provided such that it furtherforms a removal trocar, in which case the threading 7 of the pin 1 b isnot necessary. In this precise case, the guide head 2 does not compriseany portion having a polygonal section, since the sole trocar does notcomprise any cooperating means capable of acting as a key.

1. A trocar for removing an endosteal guide pin for preparing a guidepath for the implantation of a pedicle or orthopaedic screw, the pinincluding a head intended to be provisionally implanted in a bone, and aguide rod, coaxial with and rigidly connected to the head, ending in afree end adapted such that it is at least flush with the skin surface ofthe patient when the pin is in the implanted position in the bone, whichpin includes a first coupling means intended to ensure the rigidconnection thereof to and the disconnection thereof from at least onepart of a positioning trocar, and a second coupling means intended atleast to ensure the rigid connection thereof to a removal trocar,wherein it includes a hollow fixing rod intended to be fitted around theguide rod of said pin, and a coupling means cooperating with the secondcoupling means of said pin to form a removable rigid connection systemenabling the guide pin to be removed when the second coupling means ofthe pin and the cooperating coupling means of the hollow rod of theremoval trocar are assembled together, and said first coupling meansfurther comprises a rotation locking element provided on the head of theguide pin.
 2. The removal trocar according to claim 1, wherein thecooperating coupling means is formed by a tapping made on the insideface of the hollow rod, and which is capable of being assembled with thesecond coupling means of the guide pin formed by a threading made on theguide rod or on the end part of the head rigidly connected to the guiderod.
 3. The removal trocar according to claim 1, wherein the guide rodof the guide pin is capable of being cut so that the end thereof islocated beneath and in the vicinity of the skin surface when the pin isin the implanted position in the bone.
 4. The removal trocar accordingto claim 1, wherein at least one part of the head has a circular sectionwith an average diameter D1, and wherein the guide rod has a circularsection with an average diameter D2 that is less than the diameter D1 ofthe head.
 5. The removal trocar according to claim 1, wherein the guidepin is made of stainless steel or titanium, and the diameter D2 of theguide rod is less than 2 millimetres.
 6. The removal trocar according toclaim 1, wherein the head has a free end formed by a bevel, double bevelor diamond tip.
 7. The removal trocar according to claim 1, wherein therotation locking element has a polygon-shaped section.
 8. The removaltrocar according to claim 1, wherein the rotation locking elementincludes a smooth part and a threaded part also forming the secondcoupling means.
 9. The removal trocar according to claim 1, wherein thefirst and second coupling means are aligned.
 10. The removal trocaraccording to claim 1, wherein the locking element has a hexagonalsection.
 11. The removal trocar according to claim 8, wherein thethreaded part is made on a portion of the head close to the guide rodand having a polygonal section, such that said portion comprises athreading and a hexagonal smooth part.
 12. The removal trocar accordingto claim 1, wherein a portion of the head has a polygonal profilesection and the rest of the head has a circular section, and thediameter of the portion of the head having a circular section is greaterthan the diameter of the portion of the head having a polygonal section,such that a shoulder is present at the junction between said twoportions.
 13. The removal trocar according to claim 1, wherein thehollow rod ends, at one of the ends thereof, in a grasping handle. 14.The removal trocar according to claim 1, wherein the hollow rod ends, atone of the ends thereof, in means for cooperating with a power tool forproviding power-assisted placement and removal of the trocar.
 15. Theremoval trocar according to claim 14, wherein the means for cooperatingwith a power tool are formed by a rotating member rigidly connected to afree end of the removal trocar and intended to cooperate with an endpiece forming a key of the power tool.
 16. The removal trocar accordingto claim 15, wherein the rotating member has a polygon-shaped section inorder to ensure the engagement of the rotating member with the end pieceof a power screwdriver.
 17. The removal trocar according to claim 16,wherein the rotating member has a hexagonal section.
 18. The removaltrocar according to claim 1, wherein the end opposite a tip of the headof the guide pin comprises a male part of a bayonet rigid connectionsystem which is intended to cooperate with a female part of a bayonetrigid connection system provided on the removal trocar.